The present invention relates generally to vehicle monitoring systems and, more particularly, to an apparatus and method for automatically determining the state, city, province or other defined geographic entity that a vehicle is in given its latitudinal and longitudinal coordinate location.
With the advent of vehicle fleet management and monitoring systems, elaborate computerized communication systems directed at automatically obtaining and recording vehicle location and a wide variety of other information as a vehicle covers its route, numerous on-board computer systems have evolved. The information collected by these systems can be used for a myriad of purposes which encompass automated customer billing systems, computerized dispatching, trip reporting and other such tasks. One type of information available from an on-board vehicle computer is the present location of the vehicle in terms of its geographic latitude and longitude coordinates. One particularly prevalent way of obtaining this data is through a global positioning system (GPS) receiver which obtains this positional data from signals transmitted by satellite.
However, oftentimes it is necessary to convert the raw coordinate data into a more useful form which provides additional information such as what state, city, province, county or other defined geographical territory the vehicle is in. This information is particularly useful in various fleet and trucking applications such as in performing automated road use tax calculations as well as various trip reporting functions. However, even when coordinate data for the boundary lines of various geographic entities has been pre-stored in memory, the process of individually comparing the current location coordinates to boundary coordinate data for each entity, in order to determine whether the current point lies within that boundary, can become quite computer intensive.
The present apparatus and method provide a more convenient and faster way to determine what state, or other such geographic entity, a vehicle is in given its latitude and longitude coordinates. Comparing the current coordinates to sets of opposing coordinate extremes can be used to provide a gross approximation of the current geographic entity, or at least limit the possibilities to only a few. For each of the possible entities the angles created by radial lines extending from the current coordinate point to consecutive adjacent pairs of points along the entity boundary can be summed. If the current point lies within that boundary, the answer resulting from the summation (in radians) will be two times pi (2.pi.), otherwise the answer is zero.
This method thereby reduces the computational intensity of determining which of a multiplicity of entities a vehicle is currently located in. This increases overall efficiency in vehicle monitoring systems and can provide a positive confirmation of vehicle location. The present system and method operate without any driver intervention and can simplify or eliminate current driver record keeping tasks. In addition, the information provided can be combined with other data available on-board a vehicle to further increase fleet management functionality.